The present invention relates generally to nanolithography and specifically to a polymer electrostatic nanolithography method based upon Z-lift electrostatic Atomic Force Microscopy (AFM).
The use of nano and micro-scale structuring of polymers, whether as a sacrificial, pattern-transfer layer or as the active component in a nano-device, is integral to nearly every aspect of future material fabrication. Two general areas of interest are polymer patterning for micro/nanofabrication and ultra dense data storage. It is known that a fundamental limitation for the density of magnetic storage media such as computer floppy disks and the like is the so-called superparamagnetic limit that is related to spin-spin interactions. Ultra compact data storage in thin polymer films is a promising alternative to ferromagnetic storage mediums because polymer data storage overcomes this fundamental limitation, enabling ultra dense storage.
Techniques providing nanoscale patterning and feature formation are key to advances in nanotechnology, and enable the realization of nanodevices including the above ultra-dense memory, single molecule electronics and bio-nano electromechanical systems. The most versatile platform for nano-patterning is based on Scanning Probe Microscopies (SPMs), which provide for single atom placement, local chemical and physical modification (e.g. dip pen lithography), material removal, and reshaping of a substrate. With the recent introduction of massively parallel arrays of over 1024 individually addressable AFM tips, SPM techniques have drastically increased the accessible patterning speed per area, opening potential commercial opportunities and continuing the drive to develop new variations of SPM techniques. Utilizing polymer as a substrate provides the ability to re-shape the surface topology without removing or depositing material, thereby creating possible alternatives to magnetic-based technologies for use in multiple read-write storage media.
Recent nanolithography investigations pursuant to the above have been based on the spatially selective removal or deposition of polymer. While somewhat successful, the prior art techniques are generally slow to perform. These techniques generally require chemical cross-linking, and/or substantial polymer degradation or ablation to effect. This permanently changes the composition and structure of the media itself, rendering it ineffective for repetitive data storage and retrieval applications.
One such recent polymer nanolithography technique is described in U.S. Pat. No. 6,249,747 to Binning et al. The Binning device utilizes a cantilevered tip within an Atomic Force Microscope wherein an electrically conductive tip is a part of the cantilever. In use, an electric current is applied to the electrically conductive cantilever, heating the cantilever and the tip, in turn. The tip, thus heated, is selectively applied to a heat deformable film to create pits. The pits are utilized to convey information by the creation of a coherent structure. While this technique is somewhat effective, it has the disadvantage that a specialized tip is required and the application of current to heat the tip slows the overall lithographic process because the cantilever is large, requiring additional time to cool down. This technique has the additional disadvantages that the size of the structures formed is limited to the diameter of the tip (≧20 nm) and that only pits or holes can be patterned within the polymer film.
A need exists therefore for a high speed polymer nanolithography method that facilitates rapid polymer feature creation without polymer degradation, cross-linking or removal. Such a method would enable reliable, high speed feature creation, and additionally provide for a ready erasure process and subsequent re-patterning of the polymer film.